| 1. |
- Ajdari, Sima, 1985, et al.
(författare)
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Formation and Control of NOx and SOx in Pressurized Oxy-Combustion Systems
- 2015
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Ingår i: The Proceedings of the 40th International Technical Conference on Clean Coal & Fuel Systems, 31 May-4 June 2015, Clearwater, Florida, USA.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The formation and control of NOx and SOx in pressurized oxy-fuel combustion systems is discussed in the present work. The chemistry of nitrogen and sulfur species under pressurized conditions and the experiences gained from operating atmospheric oxy-fuel combustion pilot plants are reviewed in brief. In a conventional combustion and gas cleaning process, SO2 and NO are the principle NOx and SOx species. However, the oxidation of NO to NO2 and SO2 to SO3 is favored by low temperature and high pressure. In the present paper we will make a first modelling based of the altered oxidation conditions during both high and low temperature conditions in pressurized oxy-combustion. Besides the gas-phase oxidation, the liquid-phase N-S interactions will further enhance the formation of acids in the flue gas condensate. Thus, these low and high temperature processes will be discussed in the present work due to their relevance for the design of the flue gas compression and gas cleaning system in pressurized oxy-combustion.
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| 2. |
- Ajdari, Sima, 1985, et al.
(författare)
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Modeling the Nitrogen and Sulfur Chemistry in Pressurized Flue Gas Systems
- 2015
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Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 1520-5045 .- 0888-5885. ; 54:4, s. 1216-1227
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Tidskriftsartikel (refereegranskat)abstract
- A rate-based model is developed to elucidate the chemistry behind the simultaneous absorption of NOx and SOx under pressurized conditions (pressures up to 30 bar) that are applicable to the flue gases obtained from CO2 capture systems. The studied flue gas conditions are relevant to oxy-fuel and chemical-looping combustion systems. The kinetics of the reactions implemented in the model is based on a thorough review of the literature. The chemistry of nitrogen, sulfur, and N-S interactions are evaluated in detail, and the most important reaction pathways are discussed. The effects of pH, pressure, and flue-gas composition on the liquid-phase chemistry are also examined and discussed. Simulations that use existing kinetic data reveal that the pH level has a strong influence on the reaction pathway that is followed and the types of products that are formed in the liquid phase. In addition, the pressure level and the presence of NOx significantly affect the removal of SO2 from the flue gas.
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| 3. |
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| 4. |
- Cheng, M., et al.
(författare)
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Oxidation of Ammonia by Ilmenite under Conditions Relevant to Chemical-Looping Combustion
- 2015
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Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 1520-5029 .- 0887-0624. ; 29:12, s. 8126-8134
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Tidskriftsartikel (refereegranskat)abstract
- The oxidation of ammonia to NOx and N-2 was investigated under conditions that pertain to the fuel reactor during the chemical-lopping combustion of coal with ilmenite. The catalytic decomposition of NH3, the oxidation of NH3 over ihnenite, and the reduction of NO by reduced ilmenite and NH3 were studied experimentally. The catalytic decomposition of NH3, NO reduction by NH3, and reduced ilmenite were found to be important for N-2 formation. NH3 oxidation over ilmenite was the only way in which NO could be formed in this systerri, with around 18% the NH3 being converted to NO at 850-950 degrees C, The oxidation of NH3 was only slightly influenced by the reactor temperature but was strongly influenced by the concentrations of NH3 and syngas. NO formation was,promoted by high concentrations of NH3 and decreased by high concentrations of syngas. The selectivity of the NH3 toward-NO formation was favored at low concentrations of NH3 and syngas. The conversion of NH3 was complete in most cases, although 15-25% of the NH3 was not converted when the inlet syngas concentration increased to levels higher than 10-30%.
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| 5. |
- Edland, Rikard, 1990, et al.
(författare)
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Formation of nitrogen oxides in rotary kiln burners: an assessment of pilot scale experiments using gaseous, liquid and solid fuels
- 2015
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Ingår i: INFUB 2015.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The combustion process in rotary kilns for iron ore production is associated with high temperatures and large amounts of highly preheated air (λ=5-6). These conditions are favourable for NOx formation. Further, coal is typically the main fuel in the process and the CO2 emissions need to be reduced. Thus, emission control strategies are becoming of increasing importance for this type of industrial processes. The present work studies the formation of NOx during combustion of oil, gas, two coals and different blends of coal and biomass. The paper includes both experimental and modelling work. The experiments were performed in co-operation with LKAB using their pilot scale burner test facility (400 kWfuel), which is able to simulate the conditions of the full-scale process. The model, which is used to interpret the experimental results, is based on detailed reaction kinetics with simplified descriptions of temperature and mixing profiles. The results show that oil and gas flames lead to significantly higher NOx formation than solid fuel flames. In general, the thermal formation route is shown to be an important contributor to NOx formation, i.e. also for the solid fuels.
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| 6. |
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| 7. |
- Jilvero, Henrik, 1984, et al.
(författare)
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Ammonia-based post combustion - The techno-economics of controlling ammonia emissions
- 2015
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Ingår i: International Journal of Greenhouse Gas Control. - : Elsevier BV. - 1750-5836. ; 37, s. 441-450
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Tidskriftsartikel (refereegranskat)abstract
- An important process consideration in ammonia-based, post-combustion CO2 capture is the volatility of ammonia. Consequently, there is a need to adopt control measures to minimize the emission (the slip) of ammonia from such processes. This work evaluates techno-economic aspects of methods to reduce the ammonia slip. The emission of ammonia is required to be below 10 ppm while the ammonia slip from the absorber in an ammonia-based process may exceed 10%. The ammonia control methods that are evaluated in this work are staged absorption, ammonia abatement cycle, chilled absorption and acid wash. The control methods are also evaluated with respect to local conditions, such as cooling water temperature and flue gas CO2 concentration. Rate- and equilibrium-based thermodynamic modelling forms the basis for the evaluation process. A simplified economic estimation method is used to evaluate the utility cost of ammonia control designs under different operating conditions. The economic estimation shows that for the best case conditions the utility cost are as low as 1.5(sic)/tCO(2). However, the cost of the ammonia control may be more than tenfold when the available cooling water temperature is increased (>5 degrees) or when the flue gas CO2 concentration is decreased (
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| 8. |
- Jilvero, Henrik, 1984, et al.
(författare)
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Equilibrium measurements of the NH3-CO2-H2O system - measurement and evaluation of vapor-liquid equilibrium data at low temperatures
- 2015
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Ingår i: Fluid Phase Equilibria. - : Elsevier BV. - 0378-3812. ; 385, s. 237-247
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Tidskriftsartikel (refereegranskat)abstract
- The equilibrium behavior of carbon dioxide (CO2) in aqueous ammonia at low temperatures was studied by means of experiments and modeling. The low-temperature conditions of this system are of interest for the development of ammonia-based CO2 capture. This study includes experimental analyses of the vapor and liquid phases to determine the fate of CO2 in aqueous ammonia. The partial pressure of CO2 at equilibrium was measured in a gas chromatograph. The vapor phase was assessed with ammonia concentrations at 5 and 10 wt%, CO2-loadings in the range of 0.15-0.75, and at the temperatures of 10 degrees C, 20 degrees C, and 40 degrees C. The liquid-phase carbon distribution was determined based on Raman spectroscopy and partial least-squares regression modeling. Speciation of the liquid phase was determined at 5 wt% and 10 wt%, CO2-loadings in the range of 0-0.6, and room temperature (25 degrees C). Two thermodynamic models of the NH3-CO2-H2O system were evaluated with respect to the measured data. For the prediction of the partial pressure of CO2, the model devised by Que and Chen [6] proved to be the most accurate, while for the liquid-phase predictions, there was no significant difference between the models in terms of accuracy.
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| 9. |
- Òsk Gardarsdòttir, Stefanìa, 1987, et al.
(författare)
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Post combustion CO2 capture applied to a state-of-the-art coal-fired power plant - the influence of dynamic process conditions
- 2015
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Ingår i: International Journal of Greenhouse Gas Control. - : Elsevier BV. - 1750-5836. ; 33, s. 51-62
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Tidskriftsartikel (refereegranskat)abstract
- A dynamic model of the amine-based CO2-capture process is presented and applied to investigate the transient behavior of the absorption system during and after load changes in Nordjyllandsværket, a state-of-the-art coal-fired power plant with a thermal efficiency of 47.5%. Two scenarios of flexible operation in the power plant are investigated: part-load and peak load operation. Simulations of the load-variation scenarios show that implementation of active control strategies improves capture system performance with respect to capture efficiency and the heat requirement. The reboiler duty can be decreased considerably during part load operation compared to a case where no control strategy is applied. Integration of the capture process with the power plant results in an efficiency decrease of around 9 percentage points at full load and in the range of 8–12 percentage points during 60% part load operation, depending on if a process controller is used or not. Energy requirement for CO2 compression is not included in these numbers. In addition, the response time of the absorption system is significantly decreased in the cases where a process control strategy is implemented, both for part load and peak load operation
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| 10. |
- Òsk Gardarsdòttir, Stefanìa, 1987, et al.
(författare)
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Post-combustion CO2 capture using monoethanolamine and ammonia solvents: The influence of the CO2 concentration on the technical performance
- 2015
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Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 1520-5045 .- 0888-5885. ; 54:2, s. 681-690
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Tidskriftsartikel (refereegranskat)abstract
- In this study, we investigate the effects of a wide range of carbon dioxide (CO2) concentrations in flue gas on postcombustion capture of CO2 using chemical absorption with monoethanolamine (MEA) and ammonia. The applied range of flue gas CO2 concentrations represents typical profiles of emission sources associated with industrial applications. Modeling of the process chemistry to study the effect on process performance reveals that with an appropriate design of the capture process, the specific heat requirement for solvent regeneration decreases as the CO2 content of the flue gas increases. At the same time, the specific cooling requirement of the process increases and the appropriate shape of the temperature profile in the absorber becomes critical at high flue gas CO2 concentrations, especially when using MEA as absorbent, which has high reactivity and a high heat of reaction compared with ammonia. For both solvents investigated it is difficult to achieve high capture rates at low concentrations of CO2.
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